gistfile1.rb

# http://www.mikeperham.com/2009/01/21/testing-multipart-upload-with-sinatra/
module FiveRuns
  module Multipart
    class FileUpload
    
      BOUNDARY_ROOT = 'B0UND~F0R~UPL0AD'
    
      attr_reader :file, :params, :rack_opts
      def initialize(params={}, rack_opts = {})
        @to_s = nil
        @params    = params
        @key_stack = []
        @name_stack = []
        rack_opts[:content_type] ||= 'application/octet-stream'
        rack_opts[:filename] ||= 'uploaded.file'
        @rack_opts = rack_opts
      end
    
      def content_type
        %(multipart/form-data, boundary="#{boundary}")
      end
    
      def to_s
        @to_s ||= %(#{form}\r\n#{separator}--)
      end

      ########
      # private
      ########
      
      def boundary
        "#{BOUNDARY_ROOT}*#{nonce}"
      end
      
      def parts(context=params)
        r = context.map do |name, value|
          if value.is_a?(Hash)
            @key_stack.push(name)
            parts(value)
          elsif value.nil?
            nil
          else
            name = nest(name) unless @key_stack.empty?
            boundarize(name, value)
          end
        end
        @key_stack.pop
        return r
      end

      def form
        parts.flatten.compact.join(crlf)
      end
      
      def boundarize(name, value)
        [separator, 
         headers_for(name, value)
        ].flatten.join(crlf) + crlf + crlf + content_of(value)
      end

      def nest(inner)
        @name_stack = @key_stack.clone if @name_stack.empty?
        name = "#{@name_stack.pop}[#{inner}]"
        name = nest(name) unless @name_stack.empty?
        return name
      end

      def separator
        %(--#{boundary})
      end
      
      def crlf
        @crlf ||= "\r\n"
      end
      
      def headers_for(name, value)
        if value.respond_to?(:read)
          [
            %(Content-Disposition: form-data; name="#{name}"; filename="#{@rack_opts.delete(:filename)}"),
            %(Content-Transfer-Encoding: binary),
            %(Content-Type: #{@rack_opts.delete(:content_type)})
          ]
        else
          [ %(Content-Disposition: form-data; name="#{name}") ]
        end
      end
      
      def nonce( time = Time.now.utc )
        @nonce ||= (time.to_f * 1000).to_i
      end
      
      def content_of(value)
        value.respond_to?(:read) ? value.read : value.to_s
      end
    end
  end
end